SQLite Release 3.6.21 On 2009-12-07

Performance optimizations targeting a specific use case from
a single high-profile user of SQLite. A 12% reduction in the number of
CPU operations is achieved (as measured by Valgrind). Actual performance
improvements in practice may vary depending on workload. Changes
include:

The ifnull() and coalesce() SQL functions are now implemented
using in-line VDBE code rather than calling external functions, so that
unused arguments need never be evaluated.

The substr() SQL function does not bother to measure the length
its entire input string if it is only computing a prefix